Rate constants associated with changes in sodium conductance in axons perfused with sodium fluoride

摘要: 1. Membrane currents during step depolarizations were measured in axons which perfused with 300 mM-NaF and placed K-free artificial sea-water, -0.3-4 degrees C. The Na conductance was fitted by the modified Hodgkin-Huxley model, g(Na) = g(Na)m(3)(h(1) + h(2)). Changes h(1) h(2) assumed to follow [Formula: see text] where x represents inactive state.2. rate constants steady-state values for m agreement equations except that experimental relationship of m(infinity) (3) against V shifted 10-15 mV negative direction. This discrepancy, not found an experiment choline can be explained on basis a resistance series membrane between voltage measuring electrodes.3. At 0 C (in msec(-1)) associated changes using following equations: beta(h1) 0.5/{exp [- (V 32)/10] D(1)exp (- V/V(1))}, alpha(h2) pexp (V/V(2)), beta(h2) (V/V(2) - V/23.5) pD(2), condition at mV, (alpha(h2) beta(h2)) p(D(2) 2) 0.55 msec(-1). experiments gave average D(1) 3.6, V(1) 240 p 0.08 msec(-1) V(2) 70 mV. value 66 mmho/cm(2).4. voltages is steep, points alpha(h2)/beta(h2) from sea-water well above whereas data axon were. These discrepancies resistance.5. Measurements made 16-17 indicated has Q(10) 1.6, tau(m) (-1) 2.8 3.5. ratio decreased relative could 0.6.6. 250 50 mM-KF inside very similar those obtained mM-NaF. Perfusion appeared double beta(h1), mM-NaF, reduce about half.7. dependence makes it likely depolarization recovery state occurs via --> rather than h(1).